In Oracle10g and onwards, we have the option to shrink a segment that helps to manage space more efficiently.  Shrink operations can be performed only on segments in locally managed tablespaces with ASSM.

The segment advisor will highlight any segments that can be shrunk and then you can do the following steps to shrink the object to free up space in the tablespace.

Example

Enable row movement for the table.

SYS@test> ALTER TABLE TEST.TEST_AUDIT_DETAIL ENABLE ROW MOVEMENT;

Table altered.

Shrink table but don’t want to shrink HWM

SYS@test> ALTER TABLE TEST.TEST_AUDIT_DETAIL SHRINK SPACE COMPACT;

Table altered.

Shrink table and HWM too

SYS@test> ALTER TABLE TEST.TEST_AUDIT_DETAIL SHRINK SPACE;

Table altered.

Disable row movement for the table

SYS@test> ALTER TABLE TEST.TEST_AUDIT_DETAIL DISABLE ROW MOVEMENT;

Table altered.

See oracle note: 242090.1 for more options and additional detail